.content {
    width: 800px;
    margin: 100px auto 0;
}
#btn {
    background-color: blue;
    margin-bottom: 10px;
    width: 60px;
    padding: 5px;
    text-align: center;
    color: #fff;
}
#oUl li {
    width: 60px;
    height: 60px;
    margin-top: 10px;
    background-color: #777;
}